Pizza quality varies wildly in America. There are a lot of places where the only "fresh pizza" you will find is something from one of the big chains. And there are a lot of places that serve pizza that just serve terrible quick food in general, so not surprising the pizza will be bad too.

Having said that, there is a lot of good Pizza in the US, especially in areas with heavy Italian immigrations like the north east. Obviously its a different style than most Italian Pizza, but its still really good.

I have only been to Italy once for three weeks to visit my cousins, but I read a lot about pizza. From what I have read/watched from Italian sources, even Pizza in Italy was in somewhat of a rut ~20+ years ago.